The present invention is related to an end effector mounted on a robot for handling particular items, particularly a stack of flattened un-erected carton blanks.
An end effector is a device connected to a robot or other automated mechanical device for the handling of particular items during large volume or mass production operations. In one particular situation, an end effector is used in handling a stack or log of flat, un-erected carton blanks. Each carton blank is generally planar and may be constructed of paper board or the like. Examples of the uses for such cartons are as a cereal box or numerous other packages for food items.
The flattened carton blanks may be flexible in response to a compressive force applied to opposing side edges of the blank. The log or stack includes a plurality of similarly oriented blanks with the side edges of the blanks aligned and the planar faces of the blanks juxtaposed to, i.e., facing, one another. The stack or log of carton blanks may be contained in a cardboard box or tote which is used to transfer the blanks from a first location where they are manufactured to a second location where they may be individually erected and filled for shipment. Accordingly, the blanks as they exist in the tote or box may be glued but are in their flattened or non-erected state. The blanks must be removed from the tote and transferred to another machine for further processing, such as a carton magazine, conveyor, feeder, rack or the like. Typically, a robot having an end effector for handling, lifting or manipulating this stack of blanks is used for this transfer.
In order to remove the stack of blanks from the tote or box it is generally known to capture the stack of cartons with an end effector and then invert the stack so that the tote or box is on top thereof and can be lifted from the blanks. Prior to inverting the blank filled tote, swingable gates or doors are disposed over the top of the stack of cartons so that when the stack is inverted the swingable gates or doors support what is now the bottom of the stack of blanks to keep them from falling. The gates or doors then are operated as "bombay" type doors which open to deposit the stack at the next station for further processing.
However, the process of capturing the stack of blanks with the end effector as described and then inverting the stack in order to remove them from the tote or box has proven to be complicated and troublesome. Specifically, the involved operations of inverting the stack in order to remove the tote and supporting the inverted stack with gates positioned on the bottom thereof require a very sophisticated and costly end effector to carry out this complicated carton handling procedure. As a result, the end effector is costly to acquire and may be prone to failure after prolonged use presenting maintenance problems involving extensive downtime at the production facility.
In another known system for removing the stack of blanks from the tote, faces of the two outer most blanks are squeezed between opposing clamps. Only the outermost blanks are contacted by the clamps so the clamps must exert a very large compressive force on the stack in order to lift all of the blanks. One problem associated with this type of system is the large force which must be generated between the clamps to lift the stack. Such a large force may damage or mutilate at least the outermost blanks if not others in the stack. Another limitation of such a system is that even with large compressive forces, the number of blanks in the stack which can be handled is limited. Since only the faces of the outermost blanks are contacted by the clamps, the compressive force generated by the clamps in combination with the frictional interaction between adjacent blanks on the interior of the stack is required to lift the entire stack. If the stack is too large then the interior blanks will begin to fall from the stack during lifting and the remaining blanks will follow. As a result, this known system is limited in the number of blanks which can be lifted in a single operation.
Therefore, it has been an objective of this invention to provide an improved end effector for handling a stack of flattened un-erected and individually flexible cartons.
It has been a further objective of the invention to provide such an end effector which does not require inverting the carton-filled tote in order to remove the blanks therefrom for transfer to a subsequent station.
It has been a further objective of this invention to provide such an end effector which is capable of handling a high volume of operations in a timely manner without the high maintenance and complicated operations required of known end effectors.